[Story]: Source filter in the chat

[adoLime]

User Story

As a user, I want to restrict answers to specific sources / time ranges, so that I can query targeted areas.

Context & Motivation

• Type: Functional
• Parent epic: 04 EPIC - Knowledge Layer, RAG & Source Citation #53

Acceptance Criteria

• Filters "github repo only / jira board / upload" available
• Time filter "latest" / "last 6 months"

Sub-Tasks (by team)

• Backend — filter params on the query API (source type, time range)
• Frontend — filter controls in the chat (docs / code / tickets / repo, time range)
• AI — apply the filters to retrieval so only matching sources are used